Facebook CEO Mark Zuckerberg is under increasing pressure to face European Union lawmakers over the recent privacy scandal that has engulfed his company.

The President of the European Parliament, Antonio Tajani, has called on Zuckerberg to appear for questioning, adding that sending another executive would not be sufficient.

“Let me also stress that one of the Parliament’s future priorities will be to reinforce the regulatory framework to ensure a well-functioning digital market with high-level protection for our citizens,” he wrote in a letter to Facebook.

The body’s Justice Commissioner, Vera Jourova, also urged Zuckerberg to attend the parliament following a conversation with Facebook COO Sheryl Sandberg.

“This case is too important to treat as business as usual,” Jourova said this week. “I advised Sheryl Sandberg that Zuckerberg should accept the invitation from the European Parliament. [EU digital chief] Andrius Ansip refers to the invitation as a measure of rebuilding trust.”

Manfred Weber, leader of the right-wing European People’s Party (EPP) bloc, also urged Zuckerberg not to “underestimate” the parliament’s capacity to impose stricter data regulation.

“He must not underestimate the capacity of the European Parliament to do actions against Facebook and against him as CEO of Facebook.”

The calls follow the major scandal at the company over their selling of data to Cambridge Analytica, which is estimated to have affected around three million Europeans.

Last week, Zuckerberg testified before the Senate Judiciary and Commerce Committees, where he faced hundreds of questions on issues such as privacy, censorship, and monopolization.